Skepticism

EVENTS

How am I going to fit an MRI in the bedroom?

Maybe you’ve seen this before: it’s a diagram of the sensory and motor cortex of the brain, with a little man or homunculus drawn over it to illustrate the somatic areas associated with each region. You see where the little man’s knee is on the left image of the sensory cortex? Stick an electrode in there and zap it, and a patient/victim will feel a sensation in his knee. Put the patient in an MRI and tickle his knee, and that region of the brain will light up. Cool, huh?

Another cute feature: look in the medial longitudinal fissure. You see the homunculus’s toes, and right down there, located beyond the toes, is where the genital sensory area is located. Poke at that with an electrode and…we’re talking happy time at the Mad Scientists’ convention. But notice, though, that in the diagram of the homunculus, the poor creature’s genitals are drawn, and they’re male. It’s a bit sexist, don’t you think?

a team led by Lars Michels at University Children’s Hospital in Zurich, Switzerland, used functional magnetic resonance imaging to confirm that the position of the clitoris on the homunculus was in approximately the same position as the penis in men. Barry Komisaruk at Rutgers University in Newark, New Jersey, and his colleagues have now used the same method to map the position of the clitoris, vagina and cervix on the sensory cortex as women stimulated themselves.

I read these things, and I think to myself that I really went into the wrong research field. Oh, well.

They also discovered something else.

Komisaruk also checked what happened when women’s nipples were stimulated, and was surprised to find that in addition to the chest area of the cortex lighting up, the genital area was also activated. “When I tell my male neuroscientist colleagues about this, they say: ‘Wow, that’s an exception to the classical homunculus,'” he says. “But when I tell the women they say: ‘Well, yeah?'” It may help explain why a lot of women claim that nipple stimulation is erotic, he adds.

Now, as a true nerd and as a typical male who has always been mystified by the female sexual response, I feel a deep craving to plumb the mysteries with my own personal fMRI scanner. It’ll also be a research project that will go over well at the next Mad Scientists’ convention.

This reminded me of some show where two neighbors are trying to one up each other and when one gets an MRI in his house the other guy gets two until they each have an MRI or two in each room in the house.
can’t remember where I saw it.

The adjacency of the genital and foot areas and some wiring that may, in some folks, criss-cross between ’em has been suggested as the neural correlate of foot fetishism! Which would be another completely awesome research project.

What are you, simple? The way a woman’s breasts are considered by anyone has nothing to do with how they feel to the woman. Christ.

The way the woman’s breasts are considered by society might not change how they feel to the woman. I was suggesting that a culturally defined notions of what constitutes an erogenous zone, once internalized by the woman, could rewire the senso-somatic areas of the brain.

Caine, I wouldn’t jump to the conclusion of ruling out all cultural/experiential influence on the homonculus. If a person uses a particular part of their body a lot or not at all, the brain could adapt to dedicate more or less resources to it.

For simplicity of drawing. There’s a mirror-image motor cortical region and sensory region on each hemisphere of the brain; the right hemisphere corresponding to the left half of the body, and left to right, as usual.

Caine, the breasts aren’t considered erogenous in every culture. If it’s not Universal, that implies that there is a cultural or environmental aspect to it. We’re not saying that the cultural norms change the wiring of a woman’s brain. We’re saying that a woman’s internalization of those norms might alter how a woman thinks of her body. Those thoughts would then cause the re-wiring of the brain.

Jonathan, drop the fucking ‘we’. You aren’t royal, and speak for yourself.

I got it. What you aren’t getting is that outside thoughts do not affect how women feel or how they consider their own body parts in the privacy of their own heads. Repression only goes so far. The effect of touching erogenous zones when one has stayed away from that particular zone can be extremely stimulating. *shrug*

Jonathan etc: Before y’all can even joke around with cultural norms affecting someone’s own erogenous wiring, FIRST you would need to show correlation between genital sensory cortex and individual erotic zones AT ALL. We don’t know if the anus, for instance, correlates with genital-region activity any differently in people for whom it’s an erogenous zone compared to those who get nothing from it. Much less other erogenous zones or even thinking sexy thoughts. You haven’t even considered that stimulation of the exact same region by a partner is very different from self-stimulation. All of that comes BEFORE any supposed cultural influence.

I was suggesting that a culturally defined notions of what constitutes an erogenous zone, once internalized by the woman, could rewire the senso-somatic areas of the brain.

Entirely independent of culturally defined notions of erogenous zones, women nursing babies have associated physical reactions in the uterus and vagina, which contract, ending post-pregnancy bleeding more quickly and enabling the reproductive organs to return to their pre-pregnancy shape more quickly. In addition, if labor is late midwives recommend nipple stimulation can get things started.

In addition, many women report that they have feelings of pleasure when they nurse their babies, to the point where some are concerned it is ‘inappropiate’ although it’s both normal and universal. Considering how painful it can be to allow a baby to nurse, the feelings of pleasure could be an inducement to allow it, since in primitive societies children typically nurse for three years.

The fact that stimulation of the nipples is also pleasing in a sexual context may be a bonus side effect from these other far more useful benefits.

Regarding what crowepps said – that’s precisely why I’m stunned that the researchers didn’t already know that nipple stimulation has an effect on the vagina & uterus (and thus stimulates that part of the brain). It’s just so bloody obvious. Mapping it all out is pretty cool though.

Interesting. Do males generally just not display this response, then, or did they not think to test it with them?

I was going to ask the same thing. From my anecdotal experience, most men seem to get sexual kicks out of nipple stimulation as well, so I was not surprised at the results they got from women, but rather that they haven’t seen that phenomenon in men.

If they were all male researchers or childless young women, likely none of them were aware. This may be an area in which women have privilege, and precisely this sort of taking it for granted that ‘everybody knows’ is why it makes for better science (and society) to get the perspective of both genders.

Honestly, I doubt that men are different. I’ve got pierced nipples (surprise!) and one of the biggest things I discovered was how directly they were wired into my sexual response. There were a couple times where I stepped outside into a cold breeze and… Wow.

But, anyway, I think it’s more that most men aren’t comfortable with their nipples being played with because they consider it as being an inherently feminine thing to enjoy, and it doesn’t take much subconscious panic at all to completely extinguish the sexual response.

Crossposting because the whole two sites things is a bit much for me tonight and I realize that my comment might be better suited to this blog:

“It makes me happy and it also makes me sad. I mean, it’s really honestly awesome that scientists can see this, but at the same time…
why the hell does it take so long?
Women report x sensation from their nipples (which can actually be REALLY unpleasant when unwanted) and people are like eh… not really.
This reminds me of the time I sat there taking shallow breaths and trying not to black out from pain while a Dr ripped out chunks of my cervix without any painkiller because “women don’t have nerves in their cervix” and my extreme pain was apparently… uh… anecdote.
Yeah… it pisses me off.”

And to those who think women are just culturally influenced… by what?

By fucking what?

The area is sensitive, but actually that can also mean that it’s unpleasant to bother too much. Imagine too much aggressive friction on the head of your penis.

Some guys may like that, but some may find it painful because it’s too much.

FFS how many thousands, no millions, of women = ONE SINGLE MOTHERFUCKNG MALE.

Jonathan, drop the fucking ‘we’. You aren’t royal, and speak for
yourself.

Skepgineer was arguing the same point as me. You were arguing against them as well. Thus
the plural. Nothing royal about it.

I got it. What you aren’t getting is that outside thoughts do not affect how
women feel or how they consider their own body parts in the privacy of their own
heads.

That’s demonstrably untrue. Gender norms are culturally defined, internalized by
individuals, and definitely effect how women consider their bodies. If it didn’t, you
wouldn’t get disorders like anarexia. Culture itself wouldn’t be able to exist if it
couldn’t propigate within and between individuals.

Pteryxx:

FIRST you would need to show correlation between genital sensory cortex and
individual erotic zones AT ALL.

Not really. You could just scan people from other cultures. If cultural norms effect
neurology, checking different individuals from the same culture wouldn’t tell you
anything.

crowepps:

Entirely independent of culturally defined notions of erogenous zones, women
nursing babies have associated physical reactions in the uterus and vagina, which
contract, ending post-pregnancy bleeding more quickly and enabling the reproductive
organs to return to their pre-pregnancy shape more quickly. In addition, if labor is late
midwives recommend nipple stimulation can get things started.

If all those women were from Eurocentric cultures, then that’s tangential to my point.
You can’t distinguish that the congenital nature of the nipples and genitals in the
women are the source of the cultural norms or merely the consequence of it.

Considering how painful it can be to allow a baby to nurse, the feelings of
pleasure could be an inducement to allow it,

Cool story, bro. That’s the same sort of just-so story that Evolutionary Psychology gets
crticized for all the time.

The first rule of neurology is neurons that fire together, wire together. Previous
imaging studies have shown that when you think about part of your body, such as thinking
about moving your arm, the part of your brain associated with moving that arm lights up,
even though the arm itself never moves. If you repeatedly think of both your genitals
and other errogenous zones at the same time, then those areas of the brain would
cross-stimulate. This provides a plausible pathway for cultural norms to effect
neurology.

@Jonathan: “Not really. You could just scan people from other cultures. If cultural norms effect neurology, checking different individuals from the same culture wouldn’t tell you
anything.”
—

Not necessarily, because first you’d have to establish the variation range for your baseline culture; and eroticism’s both highly variable and poorly studied. I dare say you’d get more reliable results from subjects who choose what’s stimulating to them than you would from applying cultural norms to a decent-sized random sample. In this case (nipples-vs-genitals) you’re also likely to get biological effects that swamp cultural ones, where you might not for other erogenous areas.

—
“If you repeatedly think of both your genitals
and other errogenous zones at the same time, then those areas of the brain wouldcross-stimulate. This provides a plausible pathway for cultural norms to effect neurology.”
—

I’d say the failure of brainwashing/retraining programs for homosexuals indicates that cultural norms independent of individual preference aren’t all that powerful. Self-image, again, will be variable within your baseline culture.

I always figured the clitoris would be about he same size as the penis on the sensory side of these diagrams because they have about the same number of nerve endings. But I’m glad someone is doing real research to confirm this. It’s nice to know some women test subjects had a good time for science

As far as the nipple thing goes, I think both views are right. Women who are breastfeeding sometimes experience uterine contractions, so there has to be some kind of connection there, and these neural and hormonal effects may occur with other kinds of stimulation. OTOH, whether this is interpreted as sexual during these other kinds of stimulation may depend on cultural context. And I think that experience and social beliefs might “train” the brain to have a stronger sexual response to this stimulation. So everyone is right. Move along, nothing to see here.

“i hate the login” is right about the cervix. How could any doctor think it insensitive to pain when the last stages of dialation of the cervix is a huge part of the pain of childbirth? Plus I know from experience with a few partners that the cervix can be quite sensitive, sometimes in a good way and sometimes in a bad way.

I’d say the failure of brainwashing/retraining programs for homosexuals indicates that cultural norms independent of individual preference aren’t all that powerful.

You’d think, also, that attempts to “fix” fetishes would have been more successful as well.

I do remember a study that was done a long time ago (and I read about it in a book like The Man Who Mistook His Wife For A Hat ten billion years ago, so my memory may be butchering it and it may be woefully out of date) where psychologists were able to elicit a sexual response from a non sexual item by repeatedly connecting that item with something that already sexually stimulated the kids.

One thinks of those who talk about orgasmic pleasure from being beaten…

but once again that’s dealing with psychological excitement or pleasure and not stimulation.

To my understanding women report stimulation from having their nipples touched, which is not the same as pleasure.

I think also of men who report stimulation from having their prostate area touched through their anus. For some men, regardless of sexual orientation, this is pleasurable. For others, it’s freaking awful!

IOW, to say that perhaps women are “conditioned” to call that stimulation one thing and not another, or encouraged to like it in one culture while encouraged to dislike it in another would not mean anything insofar as the actual activity that is going on in the body as a result of being touched.

I don’t think Jonathan is being all *that* unreasonable. Sure, it’s speculation, but there’s pretty sound evidence for neuroplasticity in general. People who lose vision tend to re-use the visual processing part of the brain to process sounds, for example. It’s pretty cool stuff.

How much might social factors affect the brain, as compared to physical factors? Well, who knows? Some cross-cultural studies could be very interesting. Possibly best done on something more gender neutral to avoid confounding factors, though.

I’m a guy who doesn’t seem to have much pleasurable sensitivity in the nipple area. The woman who I should be in bed with right now seems to be much the opposite–with care and enthusiastic stimulus, she can have orgasms.

I don’t know how much of that is mental, but I do know she has different responses than when we were much younger–seemingly better. The classic trope is that women get less uptight with time–that may be mental, indeed.

Plasticity (things in the brain are not set in stone, and anything from cultural norms to repetitive stimulation can change perception) and variability (not all folks are wired the same way) seem to be the 2 keywords here.
Funny how reseearch does often seem to be lacking behind common knowledge. Mostly it seems to be that remnants from a male-dominated pre-20th century science have to be overcome or rewritten.

Actually, now that I think of it, one very positive way that neuroplasticity can affect sexual response is that things can be partially “rewired”. This is a rather good thing for women who’ve undergone genital mutilation, as well as for people with spinal injuries. And is attested to, for a spot of anecdata, by people such as Waris Dirie and John Callahan.

I have no problem with Jonathan speculating all he wants. Whether I should be required to listen is another matter.

When he puts his speculation – on something he may never have thought of before – ahead of the direct experience of any number of women from different cultures and those who deal with such things in their work well, then, that’s mansplaining.

And what is mansplaining? A Very Bad Thing.

For the record – when I was breastfeeding 41 years ago one of the reasons it was recommended was the beneficial effect on size and position of the uterus and on those very useful muscles we women have in our nether regions. And, behold, it was true!

We need more research and a bit less leaping to conclusions by blokes who do not have the equipment to feel those sensations. And should listen to those who do.

When my major prof. was in grad school, the homunculus he studied had no genital area. He wrote to Dr. Penfield who wrote back and answered the question. I got to see that letter when I asked about “full” cortical representation.

I don’t think Jonathan is being all *that* unreasonable. Sure, it’s speculation, but there’s pretty sound evidence for neuroplasticity in general. People who lose vision tend to re-use the visual processing part of the brain to process sounds, for example. It’s pretty cool stuff.

How much might social factors affect the brain, as compared to physical factors? Well, who knows? Some cross-cultural studies could be very interesting. Possibly best done on something more gender neutral to avoid confounding factors, though.

Cath, there’s two major problems with Jonathan’s speculation.

One is the assumption of a correlation with fucking only, when in fact, breastfeeding would have to be accounted for as well; the degree to which a boob is seen as sexual needn’t correlate with the degree to which breastfeeding is encouraged and practiced, both of which might stimulate the development of sensitivity.
Two is the assumption of cultural uniformity. Unless you have an idea of intra-cultural variation, you cannot make assumptions about inter-cultural variation; now, this could be made up by having very large sample sizes, but the nature of studies about human sex is that it deals with relatively small sample sizes. And at that point, you do need to know whether any variation you might encounter is really intercultural variation, or simply variation between individuals

I think that the reason the researchers expressed surprise was not because they had no idea that stimulating the nipples produced sexual pleasure. Instead, what was surprising was that it actually induced neural activity in the region of the cortex devoted to the genitals.

There are any number of ways that things could be wired that would produce the same effect (nipple stimulation -> arousal) without actually lighting up that bit of cortex. Our primary sensory cortices are all surrounded by association cortices that, well, associate different stimuli. And the motor responses (in this case, things like vasodilation) are moderated in entirely different areas of the brain than the somatosensory cortex.

It didn’t have to be this way to get the same result, so that fact that this is how it is might be able to tell us something interesting about how we’re built.

Obviously the connection between nipple stimulation and uterine contraction is due to cultural ideas about the erotic nature of nipples*. It couldn’t possibly be because humans are mammals and a similar mechanism has been observed in numerous other mammalian species. Humans, after all, were Specially Created, either by Culture or by a Magic Sky Fairy. I’m not arguing that culture is irrelevant, but to invoke it as a significant reason why nipples are sensitive seems simply bizarre. (Also, while nursing can be painful, it’s more painful if the kid is not latched on right and is injuring the nipple and/or not in a position to express milk from the breast. So working on avoiding the pain and/or finding a pleasurable nursing position gets the kid fed better.)

On the neuroplasticity issue, it would be interesting to investigate whether a person with spinal cord injury is more likely to remap erotic sensitivity onto parts of the body with more sensitivity to start with (i.e. the upper lip rather than the center of the forehead).

*In other words, Wimenz grow nerves in their boobs because Menz like boobs. Ridiculous.

He’s got two experiments currently running – 1 is a sex toy designed to keep someone from reaching orgasm, the other is a portable EEG to track sexual stimulation and orgasm. The site is not safe for work subject wise, and some of the images are NSFW as well, but those are usually behind cuts.

Is nobody else bothered by his saying that a lot of women “claim” that nipple stimulation is erotic? Not “report” but “claim.” It implies that he doesn’t think women are reliable reporters about our own bodies and responses: that the women in question are either mistaken or lying.

I wouldn’t call it “privilege.” It’s knowledge that hasn’t been very highly valued until recently, as you can see by the rather clueless comment by male neuroscientists in the article. In fact, as you can see in this thread, it’s still being disputed.

Also, isn’t it amazing how we hear, all the time, from EP types that all women are “wired” to be one way… until we speak up and insist that we’re actually wired to feel pleasure from a certain type of stimulation, whereupon menz decide that it must be “cultural”? I think Mattir’s summary of Jonathan’s JAQing off — “Wimenz grow nerves in their boobs because Menz like boobs” — is dead-on.

On a side note, from personal experience, I would say that erogenous nipples are very common among men. Not universal, but quite common. Still other men have sensitivity in their nipples but do not find stimulation there pleasurable.

Menyambal: “The classic trope is that women get less uptight with time–that may be mental, indeed.”

Girls and younger women are more vulnerable to negative cultural messages about their sexuality, their bodies, and other aspects of themselves that affect how they feel in the bedroom. It takes some time to work through all of that. Comfort with a long-term partner can also help.

I think Mattir’s summary of Jonathan’s JAQing off — “Wimenz grow nerves in their boobs because Menz like boobs” — is dead-on.

I’ve got to agree. I vaguely remember reading many years ago a summary of observations about a so-called ‘primitive’ equatorial tribe where women were topless and the primitive men being amused that the anthropologist looked at boobs: ho ho, very funny that he behaves like a toddler wanting to nurse — ha ha, look at the great baby wanting a mamma.

My guess is it’s the other way around, that male sexualization of the breast is more likely to be cultural, with the sensation existing because of its positive effect on child survival, a far higher evolutionary priority.

Missing the point. My point was that I wasn’t being dismissive of women’s experiences. I wasn’t implying that their experiences were imaginary.

Anyway, you were speculating, as you revealed when you conjectured “If cultural norms effect[sic] neurology”.

Yes, I was conjecturing. Which is why my first post was “I’d be interested in seeing the fMRIs from other cultures where women’s breasts aren’t considered erotic.” See that? That is a question that can be used to form a conjecture/hypothesis that can be tested by the method I outlined. I didn’t assert anything. I just stated an interesting question that occurred to me.

Affect refers to emotion. Effect refers to causation. I used the correct word. Others, including the person I was replying to did not. I had the decency not to comment on it though, as it’s (note: this is the correct usage, also) a common error and completely tangential to the actual conversation.

@Pteryxx:

Not necessarily, because first you’d have to establish the variation range for your baseline culture; and eroticism’s both highly variable and poorly studied.

You’re not studying eroticism, per se. You’re just looking at what parts of the brain light up when certain parts of the body are stimulated. In this case, there would already be a baseline established; a baseline contributed to by this very study.

I’d say the failure of brainwashing/retraining programs for homosexuals indicates that cultural norms independent of individual preference aren’t all that powerful. Self-image, again, will be variable within your baseline culture.

Considering those programs consist almost wholly of prayer and aversion therapy and are typically given to adults, I don’t think that applies. Prayer just doesn’t do anything in the first place. Adult brains are far less plastic than child brains and so less susceptible to social programming (old dogs, new tricks, and what have you). The aversion therapy would just cause homoerotic feelings to be associated with negative emotions. Considering that most people who go through such programs report increased feelings of shame and self-loathing afterwards, that part could be considered a “success”, though that seems the wrong word for it.

Francisco:

I always figured the clitoris would be about he same size as the penis on the sensory side of these diagrams because they have about the same number of nerve endings.

The clitoris has way more nerve endings than the penis. Like eight times the nerve endings. The female genitals have three times as many nerve endings as the entire male anatomy.

@I hate the login here:

I see you are compliant with them.

“Cool story, bro” is a meme. “I am aware of all internet traditions” is a meme. It’s specifically used to refer to someone who is oblivious to the use of a meme.

IOW, to say that perhaps women are “conditioned” to call that stimulation one thing and not another, or encouraged to like it in one culture while encouraged to dislike it in another would not mean anything insofar as the actual activity that is going on in the body as a result of being touched.

Not what I was saying. What I was saying is that the mental association of different body parts could result in the physical integration of those areas of the brain. The earlier this association begins, the greater the neural integration. Thus cultural mores, which would begin at the youngest possible ages, would potentially have a great impact on the wiring of the brain.

I think also of men who report stimulation from having their prostate area touched through their anus. For some men, regardless of sexual orientation, this is pleasurable. For others, it’s freaking awful!

That also has to do with the pudendal(sp?) nerve carries signals not only from the genitals but the rest of the pelvic floor as well. In a similar way, pressing on the vagus nerve through the rectum can stimulate a vasso-vagal reaction, dropping one’s blood pressure and causing one to pass out, as the vagus nerve also regulates your heart rate.

@maureen.brian:

When he puts his speculation – on something he may never have thought of before – ahead of the direct experience of any number of women from different cultures and those who deal with such things in their work well, then, that’s mansplaining.

I wasn’t putting my speculation before the direct experience of women. I made the point that if their experiences are limited to Eurocentric cultures, then those experiences would be tangential to the possibility I was suggesting.

For the record, the reason why the idea even hit me was because of a documentary I watched dealing with the fact that our culture is only one of seven cultures that regards breasts as erotic. And that 193 others do not. In those other cultures, other body parts are considered erogenous that our culture does not consider as such. You accuse me of not acknowledging women’s experience but the only reason the idea even occurred to me that culture might effect erotic perceptions was my acknowledging women’s experience.

We need more research and a bit less leaping to conclusions by blokes who do not have the equipment to feel those sensations. And should listen to those who do.

I didn’t jump to any conclusions. “I’d be interested in seeing the fMRIs from other cultures where women’s breasts aren’t considered erotic.” That’s all I said. When I was criticized for pointing that out, I replied by explaining my reasoning for why I thought that might be the case and why I’d like some evidence on the subject. Imagine that, expressing a desire for research on a topic on a science blog!

@Jadehawk:

One is the assumption of a correlation with fucking only, when in fact, breastfeeding would have to be accounted for as well;

My initial post was expressing a desire that a possible variable be accounted for. Why do you seem to think that means I don’t think other possible variables should be examined?

As a point of fact, Jonathan, the women on this blog come from / live in all corners of this planet and, to the extent that we know at all, we know they have all sorts of ethnic heritages. They have also been brought up in sub-cultures which have taught them vastly different ways to regard their own bodies. Many have completely reprogrammed themselves in adulthood but not one of these has remarked that this painful process has remapped their erogenous zones or rewired their brains.

Among the women who have commented here and the many more who will have read it a vast cry has gone up – that was a metaphor – asking, loudly, how the fuck you did not know that. You and several others have come very close to saying to women, all women, that you will not believe them until a man comes along with a study to prove it.

Hell, man, this is not Iran where if I said X is happening to my vagina I would need two witnesses – presumably living full time within my genitalia – before I could be believed.

By all means, if you can get the funding, conduct as many cross-cultural and longitudinal studies as you wish. The results could only be very interesting.

Right now you have the choice of believing the women, where there is evidence, or of positing some cultural force so vast, so uni-directional, that it could reprogram every female human between birth and her first sexual experience. For the latter there is no evidence at all.

Missing the point. My point was that I wasn’t being dismissive of women’s experiences.

Then you did it wrong, because that’s not what you wrote; what you wrote is to what I responded.

Affect refers to emotion. Effect refers to causation. I used the correct word.

Sigh.

No, you used it as a verb, hence what applies (your own source) is affect and effect.

Others, including the person I was replying to did not. I had the decency not to comment on it though, as it’s (note: this is the correct usage, also) a common error and completely tangential to the actual conversation.

Missing the point. My point was that I wasn’t being dismissive of women’s experiences.

Then you did it wrong, because that’s not what you wrote; what you wrote is to what I responded.

Affect refers to emotion. Effect refers to causation. I used the correct word.

Sigh.

No, you used it as a verb, hence what applies (your own source) is affect and effect.

Others, including the person I was replying to did not. I had the decency not to comment on it though, as it’s (note: this is the correct usage, also) a common error and completely tangential to the actual conversation.

YIKES … I just realized there is a genital region indicated on the sensory cortex and NOTHING on the motor cortex. So the brain never gives any direction to act on a penis or vagina? I suspect a bit more work is needed.

YIKES … I just realized there is a genital region indicated on the sensory cortex and NOTHING on the motor cortex. So the brain never gives any direction to act on a penis or vagina? I suspect a bit more work is needed.

The entire male genital apparatus contains one single voluntary muscle.

Of course, chances are good that that’s just me. But this doesn’t line up with the other ways in which I’m unusual: I’m unusually ticklish*, and my nipples are more sensitive than the surrounding chest, but they’re still surprisingly difficult to find by feeling through a T-shirt.

* So much so that I hate being tickled. There are people who find it funny; I don’t.

Or maybe some men do have this wiring and others don’t, and that’s why some men don’t seem to enjoy nipple stimulation.

Wouldn’t surprise me at all.

Or maybe the homunculus is wrong, and any sensation a given person finds erotic will light up the genital area.

Doesn’t strike me as implausible either.

and by Leel:

1) Nipple stimulation. My (apparently hetero) husband feels it is the most erotic sensation after direct penis stimulation, and can have an orgasm from nipple stimulation alone. I have to be careful where I stroke his chest if I don’t want a cuddle to escalate into sex.
I (female, also apparently hetero) would rather not have my nipples touched, because unless done very gently it is uncomfortable. I certainly HOPE that women have fewer and less sensitive nerves in their nipples than men, because (for me) nursing a violently sucking, and later on biting and chewing, infant would mean constant pain (and in much earlier times, abandonment of the infant).